A radial turbine is equipped with a single turbine wheel that converts swirling energy of the flow of a swirling fluid having a radial flow component as a main component and flowing into a turbine wheel to a rotational motive force and that discharges the flow that has released its energy, in an axial direction. The radial turbine converts the energy of a low/medium- or high-temperature, high-pressure fluid to a rotational motive force and is used to recover the motive force of exhausted energy of a high-temperature, high-pressure fluid exhausted from various kinds of industrial plant. Radial turbines are also used in exhaust heat recovery of systems that acquire a motive force via a heat cycle, such as power sources for ships and cars. Radial turbines are also widely used to recover a motive force in binary-cycle power generation or the like that uses a low/medium-temperature heat source, such as geothermal or OTEC.
If the various energy sources have a plurality of pressures, a plurality of turbines are used, that is, one turbine is used for one pressure source, as disclosed in PTL 1. Alternatively, two turbine wheels are sometimes provided coaxially.
This is because, turbines, for example, radial turbines, are designed for optimum conditions for the individual fluid pressures. For example, the inlet radius R of a radial turbine depends on the relation, g·H≈U 2, where g is gravitational acceleration, H is the head, and U is the turbine-wheel-inlet circumferential speed. That is, if we let the rotational speed of the turbine wheel be N (rpm), the inlet radius R is set at a value near to R≈U/2·π/(N/60).
A known example of a radial turbine that handles a fluid having a strongly fluctuating flow rate has one inlet channel partitioned by a dividing wall, as disclosed in PTL 2. This is configured such that one of the inlet channels supplies fluid to the hub side of the blades.
In this case, however, both of the inlet channels handle fluids with the same pressure. Furthermore, since the inlet channels are provided next to each other and are simply partitioned by the dividing wall, if fluids with different pressures are handled, a higher-pressure fluid flows toward a lower-pressure fluid, decreasing the turbine efficiency.